Thermostatic device



March 29, v1932. 5., K. CLARK I THERMOS'IATIC DEVICE Filed Oct. 20, 19273 Sheets-Sheet 1 INVENTOR far/K. C/Grk ATTdRNEY March 29,1932. E. K.CLARK. I 1,851, 6

THERKOSTATIC DEVI CE Filed Oct; 20,1927 3 Sheds-Sheet a ATTORNEYPatented Mar. 29, 1932 UNITED STATES PATENT. OFFICE mi. 1:. cmax, ormnsrrmn, onto, assreivoa 'ro WESTINGHOUSE rmrzo'rarc a MANUFACTURINGCOMPANY, A CORPORATION OF PENNSYLVANIA THERMOSTATIG DEVICEApplicationfiled October 20, 1927. Serial No. 227,441.

-My invention relates to thermostatic de-' vices and particularly totemperature indi: eating and controlling devices. I

An object of my invention is to provide a thermostatic device that shallbe simple in construction and efl'icient in its operation.

- And a further objectof my invention is to provide a temperatureindicatorv and controlling device that shall closely followthetemperature of a body, whether that temperature is increasing ordecreasing.

In practicing my invention, I provide a support on which an indicatorand an adjustable control pointer are pivotall mount ed. The indicatorand pointer ma e equipped with cooperating contact mem ers in order thatan electric circuit may be controlled thereby. V

A bimetallic strip is provided for actuating the indicator in accordancewith the tem erature of abody to be controlled, the strip eingyieldingly supported, at one end, by the support and having a pivotalconnection tot indicator. I

For a fuller understanding of my invention, reference may be had to thefollowing description, taken in conjunction with theaccompanying-drawings, in which Figure 1 is a View, in side elevation,of a thermostatic device embodyin my invention, Fig. 2 is a View intront 'e evation of the same device, v

Fig. 3 is a view, in section, taken on the line III-III of Fig. 1,

Fig. 4. is a view, in section, taken on the line IVIV of Fig. 2,

Fig. 5 is a view, in section, taken on the line V-V of Fig.3,

Fig. 6 is a partial front plan view ofthe device shown in Figs. 1 to 4,inclusive embodied in the door of an oven, and

Fig-7 is a top plan view, partially in section, of the showing in Fig.6. a

' In the drawings, a support 1,-of substantial- 4 1y channel shape, isprovided with integral upturned lugs 2, 3 and 4 and openings 5 and 6located at the ends thereof. The ends of the support are provided withlugs or tongues 7 and 8 that extend through end walls 9 and 10 of anopen-end casing comprising two subotally supported on a pin 17 thatextends through the portion of L-shape and the lugs 2 and 3. In orderthat a lever arm may be provided for turning the indicator 16 on itspivot pin 17 a pin 18 is provided that passes through the L-shapedportion of the indicator to the right of, and below, the pin 17, asviewed from Fig. 1. Y

The upperend of the indicator is provided with an offset portion ofsubstantially U- shape that cooperates with a scale 19 of arouate shapethat is secured to a scale support 21 which, in turn, is secured to, andsupported by, the casing at 22 and 23 byrivets or other suitable means.

The indicator is provided with a cooperating control pointer 24 that isivotally secured to the lug 4 by a rivet 25. 11 order that the pointer24 may be frictionally held in a predetermined position, a springlock'washer 26 is provided that is located between the lowerend of thepointer 24 and the lug. As in the case of the indicating pointer 16, thecontrol pointer is provided with an offset portion 27 of substantiallyU-shape at its upper. end which cooperates with the scale 19.

In order that an electric circuit may be controlled by the indicatingand control inters. 16 and 24, the pointers may be provi ed withcontacts 28 and 29, respectively (see Figs. 3 and 5). The contacts aresecured to the pointers by rivets or other suitable means and areinsulated therefrom by washers 31 of insulating material.

In order that the point of contact between the contacts 28 and 29 may beprotected from oxidation resulting from electric arcs their engagingends may be provided with silvered rivets 32. The outer ends of thecontacts 28 and 29 are provided witbflexible conductors 10b 33 and 34that are electrically connected to terminals 35 and 36, respectively,the latter being secured to the casing portions 11 and 12. The terminals35 and 36 may be insulated from the'casing by washers 37 of insulatingmaterial.

The terminals 35 and 36 being substantially similar, like parts will bedesignated by the same reference characters. These terminals comprise asubstantially cylindrical connector 38 having a rivet portion 39,extending through the walls of the casing, and a strip 40 ofsubstantially L-shape to which the flexible leads 33 and 34 may beconnected either by brazing or other suitable methods.

The connectors 38 may be insulated from the casing by the mica washers37, one of which fits into a depression in the casing and the other ofwhich is locatedbetween the casing and the strip 40. As shown, theconnectors 38 and the strips 40 are held securely together against thecasing walls by the rivet portions 39.

In order that the indicating pointer 16 may be actuated in accordancewith a thermal condition to be controlled, 2. bimetallic strip 41 isprovided. One end of the strip 41 is secured to the free end of acantilever spring 42 which, in turn, is secured to the support 1' byrivets or other suitable means. As shown in Fig. 1 of the drawings, thefree end of the cantilever spring extends downwardly through the opening5 in the support. 7

The free end of the bimetallic strip -41 is provided with a lug 44having a recess 45 therein, in which the pin 18 of the pointer 16islocated. If the bimetallic strip 41 is deflected, either in an upward orin a downward direction, as viewed from Fig. 1, the pin 18 slides in therecess 45, depending upon the direction of the deflection. As 'the stripis deflected, the pointer lflis caused to turn on its pivot pin 17. Asis evident from Fig. 2 of the drawings, if the temperature of the strip41 is increasing, the pointer 16 is caused to move up the scale 19, andif decreasing, the pointer moves in the opposite direction.

Since the point of contact between the lug 44 and the pin 18 changes asthe strip 41 is deflected, the variation in the distance between thesupported end of the strip and the point of contact between thepin 18and the lug 44 is so compensated for that the indicating pointer 16moves uniformly and substantially in direct proportion to the change intemperature of the strip.

Because the strip 41 is so secured to the spring 42 that the broad faceor edge thereof is adjacent to the wall 15 of the oven door,

' themaximum-area of the strip issubjected to the temperature of theoven wall or lining 15, which, of course, is at a temperature propor- Vtional to the temperature of the'interior' of the oven. As the maximumarea. of the strip isutilized for absorbing heat conducted to it throughwhich a handle 53 extends.

from the oven wall, the strip will be sensitive and will respond quicklyto temperature changes within the oven.

It is to be notedthat, by supporting the bimetallic strip 41, as shownin the drawings,

the strip may be positioned closely to the gagement with a supportingmember 48 that is secured to'the support 1. For convenience inmanufacturing, the spring 42 may be disposed between the support 1 andthe supporting member 48 so-that both the spring and the supportingmember may be secured to the support 1 by the same rivets or securingmeans. I

By adjusting the supported end 0f the bimetallic strip-41, the pointer16 .may be caused to indicate a temperature on the scale 19 thatcorresponds substantially to the actual temperature of the strip 41.Adjustment of the position of the pointer 16 obtained in this mannerimposes no strains or initial stresses upon the strip, because only theposition of the supported end of the bimetallic strip 41 is changed. Thestrip is not strained by'ad justing it, because it is evident that thestress I imposed is merely that of the weight of the pointer 16,whichremains substantially constant over'its range of travel.

In order that the temperature at which conpointer 16 up the scale untilthe contacts 28 and 29 engage each other, thus causing an electriccircuit (not shown) for energizing heating elements located in anelectric oven (not shown) which are well-known to those skilled in theart, to be deenergized.

The indicating and control pointers and operating mechanism disposed inthe casing may be protected fromexternal forces by a cover 49 that issecured to the top end of the casing by screws 50. The cover is providedwith a window 51, in order that the scale 19 may be visible to theoperator, and a slot 52 The handle is secured to the upper end of themoved to any redetermined position without the casing.

As shown in Fi 6 and 7 of the drawings,

the thermostatic evice illustrated in Figs. 1' to 4, inclusive, isinserted through an opening in an outer wall 56 of the oven 'door, thethermostat being secured to the inner wall 15, as previously set forthherein. When the thermostatic device is in place, an escutcheon plate 57having an opening through which the cover 49 extends, is secured to theouter wall 56 of the door. 7

, The middle portion of the escutcheon plate and the outer wall of theoven door'so interfit with the upper end of the thermostat casing thatthe openings between the ends of the co'ver'and the endwalls of thecasing are closed, thereby preventing'insulating material, locatedbetween the oven walls, from" getting into the thermostat (see Figs. 6and 7 The escutcheonplate is provided with openings 58 and 59 at itsbottom and top edges, throu h which air currents may circulate; thereore, the thermo-responsive bimetallic element 41 will not be located ina dead air space as a result of the chimney effect. produced by theescutcheon plate. The forwardly extending part of the casing ismaintained at a relativel low temperature, thus making accidenta burningof an operator practically impossible.

Since the air circulates continually about the bimetallic element, theelement will follow closely the temperature changes which take placewithin the oven. By properly pro-- portioning the dimensions of theimetallic element and properly adjusting the pivotal connections betweenits free end and the indicating pointer, the thermostatic device may becaused to follow substantially the er:- act temperature within the oven,that 15, 1f

the oven is being heated, the pointer 16 will indicate a temperature onthe-scale 19 that is substantially equal to the exact temperature withinthe oven and, if the temperature is decreasing, the pointer willindicate on the scale substantial y the exact temperature of the oven asit cools. Therefore, it is seen that the chimney effect produced bg theopenings in the escutcheon plate and t e open cas ing structure in whichthe bimetallic strip is located causesthe bimetallic member 41 to followsubstantially the exact temperature within the oven.

Various modifications may be made in the devic embodying my inventionwithout dearting from the spirit and the scope thereof. Idesire,therefore, that only such limitations shall be placed thereon as areimposed by the prior art and the appended claims. I claim as myinvention:

1. In combination, a casing, a support therein adjacent to an open endthereof, an

. rang indicator pivotally mounted on the support, and a substantiallystrai ht flat bimetallic strip having one end yiel ingly and adjustablmounted on said support and the other en pivotally connected'to saidindicator, said strip havin its broad side located closely adjacent tote open end of the casing.

2. In combination, an elongated support of substantially channel shapein lateral section, an indicator ivotally mounted thereon, andasubstantial y straight vfiat bimetallic strip located within the channel-portion of the support and having one-end 'yieldingly mounted thereonand the other end having a pin-and-slot connection with said indicator,said strip having its broad side adjacent to the support. a

3. In a thermostatic device, in combination,

a casing having an open end adapted to be located closely adjacent to aheat-receiving member whose temperature is to be indicated, an elongatedsupport extending along, and spaced from, said open end of the casing,an indicator of substantially L-shape and having legs of unequal length,pivotally mounted adjacent to one end of the elbngated support,

the longer leg extending away from the plane of the elongated support atsubstantially right angles thereto, a pin adacent to the end of theshorter leg, a

'bimetallic strip located between the support and the adjacent open endof the casing, a

resilient and adjustable mounting means for one end of the bimetallicstrip and located near the other end of the support, and a slotted lugat the other end of the bimetallic strip for receiving the pin, wherebya sub stantially uniform movement of the end of the longer leg of theindicator is obtained for equal changes in temperature over a wide 4. Ina thermostatic device adapted to be mounted in an opening in an outerwall of a double-wall oven structure, in combination, a casing having aportion adapted to extend in front of the front wall of the ovenstructure, an elongated support of channel shape in lateral sectionlocated adjacent to the rear end of the casing, a substantially straightflat bimetallic strip adjustably and resiliently secured to'theelongated sup ort near one end of the support, an indlcator pivotallymounted on the elongated support near the other end of the. support, apin-and-slot connection between the indicator and the free end of thebimetallic strip, and an arcuate scale over which the movable end of theindicator may move, said scale bein located in that part of the casingadapte to extend in front of the front wall of the oven strucure.

5. A thermostatic device for a heated apbimetallic member having one endyieldingly mounted near the other end of said support and its other endhaving a pin and slot connection with said indicator, the support beingarranged to present a broad face of the bimetal to anappliance withwhich the thermostatic device may be associated.

H 6. A thermostatic device including an elongated support having a planesurface, an indicator pivotally mounted near one end of the support, asubstantially straight flat bimetallic member having one end yieldinglymounted near the other end of the support and its other end operativelyengaging the indicator, and means-mounted on said support for adjustingthe position of the yieldingly' mounted end of said bimetallic member ina direction at right angles toits flat surface.

7. A thermostatic device including an elongated support having a planesurface, an indicator pivotally mounted near one end of said support andextending laterally away from the plane surface, a leaf spring havingone end secured near the other end-of the support and the other endunsupported, a substantially straight flat bimetallic member having oneof its ends secured to the unsupported end of said spring, a pin" andslot connection between the other end of the bimetallic member. and theindicator, and means mounted near said other end of said support andengaging the unsupported end of the leaf spring for adjusting theposition of that end of the spring and one end of the bimetallic memberin a direction at right angles to its flat surface.

8. A thermostatic device including an elongated support having a planesurface, an indicating member pivotally mounted near one end ofthesupport and extending laterally therefrom, said indicatingmemberhaving a lever arm extending .from the. pivotal mounting in a directionlongitudinally of the plane surface of the support, a pin extendingthrough said lever arm, a substantially straight fiat bimetallic memberhaving one of its ends supported near the other end of the support, anda lug secured to the other end of the bimetallic member, said lug havinga slot therein extending in a direction longitudinally of the bimetallicmember, through which said pin extends.

In testimony whereof I have hereuntosubscribed my name this 6th day ofOctober,

" EARL K. CLARK.

